examples/src/main/java/org/apache/spark/examples/sql/streaming/JavaStructuredNetworkWordCount.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.spark.examples.sql.streaming;

import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.sql.*;
import org.apache.spark.sql.streaming.StreamingQuery;

import java.util.Arrays;

/**
 * Counts words in UTF8 encoded, '\n' delimited text received from the network.
 *
 * Usage: JavaStructuredNetworkWordCount <hostname> <port>
 * <hostname> and <port> describe the TCP server that Structured Streaming
 * would connect to receive data.
 *
 * To run this on your local machine, you need to first run a Netcat server
 *    `$ nc -lk 9999`
 * and then run the example
 *    `$ bin/run-example sql.streaming.JavaStructuredNetworkWordCount
 *    localhost 9999`
 */
public final class JavaStructuredNetworkWordCount {

  public static void main(String[] args) throws Exception {
    if (args.length < 2) {
      System.err.println("Usage: JavaStructuredNetworkWordCount <hostname> <port>");
      System.exit(1);
    }

    String host = args[0];
    int port = Integer.parseInt(args[1]);

    SparkSession spark = SparkSession
      .builder()
      .appName("JavaStructuredNetworkWordCount")
      .getOrCreate();

    // Create DataFrame representing the stream of input lines from connection to host:port
    Dataset<Row> lines = spark
      .readStream()
      .format("socket")
      .option("host", host)
      .option("port", port)
      .load();

    // Split the lines into words
    Dataset<String> words = lines.as(Encoders.STRING()).flatMap(
        (FlatMapFunction<String, String>) x -> Arrays.asList(x.split(" ")).iterator(),
        Encoders.STRING());

    // Generate running word count
    Dataset<Row> wordCounts = words.groupBy("value").count();

    // Start running the query that prints the running counts to the console
    StreamingQuery query = wordCounts.writeStream()
      .outputMode("complete")
      .format("console")
      .start();

    query.awaitTermination();
  }
}
